Mr Brown publicly insisted that he had never hit anyone in his life - although the extracts contained no claims stringer than one that the PM ''roughly shoved aside'' an aide.

Lord Mandelson told BBC1's Andrew Marr Show: ''I don't think he so much bullies people as he is very demanding of people.

Mr Brown was ''a man who is quite emotional, is quite passionate in what be believes and what he is doing... who gets angry but chiefly with himself, who doesn't bully people'', he went on.

''He is demanding of himself, he is demanding of people around him, he knows what he wants to do, he does not like taking no for an answer from anyone, he will go on and on until he has got a policy and an idea in the best possible form which he can then roll out.

''There is a degree of impatience about the man but what would you like, some sort of shrinking violet at the helm of the Government when we are going through such stormy waters.''

He said an account in the book of him warning Mr Brown he could end up being the worst PM in history was ''completely untrue''.

According to Mr Rawnsley's book, the Cabinet Secretary looked into Mr Brown's behaviour after hearing about the PM pulling a typist from her chair to take over the keyboard.

''This is no way to get things done,'' the book records the civil servant telling him.

The author said today that he was ''100 per cent sure'' that Sir Gus had intervened.

''I'm sure he made his own investigations. One of the interesting things is they deny things that were not said,'' he told Sky News.

''I do not say he launched some 'formal inquiry', which would be an extraordinary thing for the Cabinet Secretary. I have no evidence of that. I say he made his own investigations and he gave a warning, a verbal warning, to the Prime Minister about his conduct and I am absolutely confident that happened - 100 per cent sure.''

''I was particularly careful in this area because it's obviously a very sensitive area to be sure that this wasn't gossip or hearsay or tittle-tattle. The sources were 24-carat - not third-hand or second-hand - first-hand sources.''

Lord Mandelson said: ''If I had to make a choice and put my money on whether Andrew Rawnsley is telling the truth or the Cabinet Secretary I would put my money on the Cabinet Secretary.''

The book risks undermining recent efforts to portray a softer side of the PM - such as in his television interview with Piers Morgan although the book was also reported to show examples of Mr Brown's skill at dealing sensitively with staff facing family emergencies and bereavements.

Earlier reports had suggested Mr Brown would be accused of hitting staff - something he vehemently denied when asked about it in the Channel 4 News interview.

''Let me just say, absolutely clearly, so that there is no misunderstanding about that: I have never, never hit anybody in my life,'' he said.

''Of course you do get angry, mostly with yourself. But I'm very strong willed, I'm very determined. I think the country wants someone that will push things forward, and not allow things to be stagnant and stale, and every morning I get up with a determination to do my best for this country,'' he said - saying the only thing he threw was papers to the floor.

Mr Rawnsley said his book also contained accounts from insiders who admired Mr Brown's handling of events, such as during the financial crisis.

Some colleagues, including ministers, had always found the Prime Minister's treatment of them "intolerable", Mr Rawnsley said, adding: "But there are other people, including some of the members of staff who have been on the receiving end of this, who still admire him nevertheless."

Harriet Harman, the Deputy Labour leader said she didn't recognise the negative portrait of Mr Brown's behaviour and hit out at the "anonymous briefings" in the book.

"These things that have been put in the book are wrong and have been denied and people will judge for themselves," she told Sky News.

"I think it's unfair to put in a book unnamed anonymous sources saying things that happened, when the people themselves concerned have not had a chance to say 'well actually that's not true'."

"He won't be a shrinking violet until the economy is fully in recovery and nobody is unemployed," she added.

"He passionately cares about things, but that's a good thing not a bad thing."

William Hague, the shadow foreign secretary said the latest claims were "part of a pattern if allegations that raise questions about the Prime Minister's judgment and behaviour".

Mr Hague said staff deserved "the highest standards" of behaviour from politicians and suggested Mr Brown was not "cut out" for the highest office.

"I don't think he has ever shown that he can lead a happy team and a successful team and maybe if there's any truth in these allegations that's part of the reason why. I think that is one of the reasons he has struggled." he told Sky News' Sunday Live.

"I don't think he has really been cut out for it."

He said: "The people who work in Number 10 or at the top of other government departments work round the clock, they are very hard working and dedicated and not very highly paid considering their hours and their responsibilities,"

"They are entitled to expect the highest standards of behaviour and courtesy and politeness from the ministers and the prime minister they serve."